Light emitting diodes (“LEDs”) and other types of light emitting devices are widely used for background illumination in electronic devices and for signage, indoor lighting, outdoor lighting, and other types of general illumination. Light emitting devices typically emit light at only one center wavelength, and thus they do not produce white light. One conventional technique for emulating white light with LEDs includes depositing a phosphor on an LED die. FIG. 1A shows a conventional light emitting device 10 that has a support 2, an LED die 4, and a phosphor 6. FIG. 1B shows an example of an LED die 4 that includes a substrate 12, an N-type gallium nitride (GaN) material 14, GaN/indium gallium nitride (InGaN) multiple quantum wells (“MQWs”) 16, a P-type GaN material 18, a first contact 20, and a second contact 22.
Referring to both FIGS. 1A and 1B, in operation, an electrical voltage is applied between the first and second contacts 20 and 22. In response to the applied voltage, the MQWs 16 of the LED die 4 produce a first emission (e.g., a blue light) that stimulates the phosphor 6 to emit a second emission (e.g., a yellow light). The combination of the first and second emissions appears generally white to human eyes if matched appropriately. As discussed in more detail below, using phosphors has certain drawbacks. Accordingly, several improvements in modifying emission of light emitting devices without using phosphors may be desirable.